Process of producing gallium



Patented Jan. 15, 1952 2,582,378 PROCESS OF PRODUCING GALLIUM Ralph Waldo Brown,

to Aluminum Company of East St. Louis, 111., assignor America, Pittsburgh,

Pa., a corporation of Pennsylvania No Drawing.

Application September 17, 1947,

Serial No. 774,687

2 Claims.

This invention relates to the production of gallium, and relates particularly to recovering gallium from alkali metal aluminate solutions. This application is a continuation-in-part of my application Serial No. 7 10,9131, filed April 11, 1947, entitled Process for Treating Alkali Metal Aluminate Solutions.

Gallium oxide can be extracted from various minerals by dissolving the gallium oxide in an aqueous alkali metal hydroxide solution, such as a 10-20 per cent solution "of sodium or potassium hydroxide. However, minerals containing'gallium oxide frequently also contain a large proportion of alumina which also dissolves in such solutions to form alkali metal aluminate. Since the percentage of gallium oxide in the ore is very small (reported analyses range from less than 0.001 per cent to 0.01 per cent), the solutions produced when dissolving gallium oxide from such ores by means of an alkali metal hydroxide solution contain a very large proportion of alkali metal aluminate and only a small proportion of dissolved gallium.

It has been stated in the'literature (Das Gal lium, by Einecke, published in 1944 by J. W. Edwards, page 92) that gallium oxide and hydroxide, dissolved in alkali metal hydroxide solutions, form alkali metal gallates which are analogous to the corresponding aluminates. Since there is, however, some uncertainly about their constitution, I have preferred to designate such an alkaline solution merely as one containing dissolved gallium, thus making no assumptions as to the actual chemical compound of gallium present in the solution.

-Ordinarily when gallium oxide is precipitated from solutions of the type mentioned above by adding an acid or acid salt to the solution, alumina also precipitates, and since the amount of alkali metal aluminate in the solution is so much larger than the amount of dissolved gallium present, the proportion of alumina to galliumoxide in the precipitate is quite large. Consequently, if it is attempted to recover metallic gallium by dissolving the precipitate in a suitable solvent and then precipitating gallium from the resulting solution by previously proposed methods, the gallium concentration of that solution is too small for economical extraction of gallium.

A method of avoiding that difliculty is described in the co-pending United States patent application of Francis C. Frary, Serial No. 739,538, filed April 5, 1947, and entitled Process of Producing Meta, in which dissolved aluminum values are insolubilized by converting alkali metal aluminate in the original galliumbearing solution to alkali metal hydroxide and precipitated calcium aluminate, while leaving the gallium in solution. After that step, gallium oxide can be precipitated from the solution by introducing an acidic material thereinto, and the precipitated gallium oxide can then be removed and dissolved in a solvent to form a solution from which metallic gallium is recovered.

I have found that precipitation of gallium oxide by the addition of an acidic material to an alkali metal hydroxide solution containing di's- Y solved gallium is facilitated if alumina is coprecipitated with the gallium oxide as a result of the presence in the solution of sufficient alkali metal aluminate to provide an atomic ratio of dissolved aluminum to dissolved gallium of at least 25:1. With lower atomic ratios of alumi-, num to gallium, precipitation of gallium oxide from the solution is much more difficult, and becomes increasingly difficult as the atomic ratio becomes smaller. On the other hand, it is preferred that the atomic ratio of aluminum to gallium in the solution be no greater than :1 in order that the proportion of alumina to gallium oxide in the precipitate produced shall be sufficiently low to minimize the cost of extraction of gallium by dissolving the precipitate and subsequently precipitating metallic gallium from the solution thus produced. By precipitating gallium oxide from a solution in which the ratio of dissolved aluminum to gallium lies withinthe above range, it is feasible to produce precipitates without difficulty which contain gallium oxide equal to 2 per cent of the weight of the alumina values in the precipitate.

Accordingly in carrying out this phase of my invention, after an alkali metal aluminate solution with gallium dissolved therein has been produced in which the atomic ratio of dissolved aluminum to gallium is greater than 100:1, part of the aluminum is insolubilized to produce a solution in which the atomic ratio of dissolved aluminum to dissolved gallium is at least 25:1, but preferably is not greater than 100:1. Such insolubilization of aluminum can be effected satisfactorily in accordance with the procedure described in the above-mentioned application of Francis 0. Frary of mixing sufficient hydrated lime or quick lime with the original solutionwhich preferably is maintained at a temperature of above 100 F.-to react with the necessary proportion of the alkali metal aluminate inthe solution and form calcium aluminate and alkali metal hydroxide, and leave a solution having a ratio of dissolved aluminum to dissolved gallium within the above-mentioned range. If the original solution contains ingredients other than alkali metal aluminate which react with the calcium compound added, it is, of course, necessary to use sufficient lime for such side reactions, as

well as for theformation of thedesired amount of calcium aluminate. Also, part of the dissolved aluminum may be precipitated as aluminum hydioxide by other known processes, if desired, before adding the calcium compoundl 3 4 After =-the-above-mentioneol precipitation of Iclaim: aluminum values from the solution, hydrous gall. The process of producing gallium comprislium oxide and alumina are co-precipitated from ing the steps of forming an aqueous alkali metal the solution by introducing an acid or acid salt aluminate solution containing dissolved gallium, into it. Next the precipitate thus produced is 5 decreasing the atomic ratio of aluminum to galdisSOlVed n an q s a i et l hydroxide lium in the resultant solution by insolubilizing solution, such as a sodium or pota sium ydro sufiicient of the dissolved aluminum values of e solution, m n an a ali tal aluminate that solution as calcium aluminate that the So ut on Cont i i di s v d gallium Metallic atomic ratio of dissolved aluminum to dissolved allium is then extracted from that solution by hi allium in the solution lies in the range of from electrodeposition. Suitable procedures for the 25:1 to 100:1, subsequently co-preclpitating galelectrodeposition of gallium from alkaline solui id n al ina from th said solution tlons are well-known and set forth in the literaby introducing an acidic material thereinte,

ture, and consequently will not be described here. solving the co-precipitated gallium oxide and alu- As the gallium concentration of the electrolyte l5 mina in an aqueous alkali metal hydroxide 1 decreases during the electrodeposition operation, m electrodepesiting part of the dissolved p m and e electrical energy is required to lium from the resultant solution as metallic galprecipitate a given amount of gallium, until ultihum, thereafter mixing t gallium-bearing eleemately further p e pitation of gall um from the trolyte from the last-mentioned step with addisolution e s uneconomical. although some tional aqueous alkali metal aluminate solution dissolved gallium still remains in the solution. containing dissolved llium, and employing the 'To recover such dissolved gallium and separate it resultant mixture i th aid second-mentioned from much of the alumina content of the elect in furthe operation of the process.

trolyte, I mix the spent electrolyte with a fur- 2 h process of producin gallium compristher quantity of alkali metal aluminate solution mg the steps of formjng' an aqueeus k li m tal containing dissolved gallium, which has been prolu jnate l ti n containing dissolved gallium d d as mentioned above by treating an Ore with in which the atomic ratio of dissolved aluminum an aqueous alkali metal hydroxide solution, and to dissolved gallium is greater than 9; 1, employ the mix in the production of further solubilizing suilioient of the dissolved aluminum metallic gallium in accordance With the procsvalues of that solution that the atomic ratio of dures already described herein. In other wo s, dissolved aluminum to dissolved gallium n th e alumina-gallium oxide ratio f the mix is solution lies in the range of from 25:1 to 100:1, a st y insolllbiliiing dissolved aluminum subsequently loo-precipitating gallium oxide and u s as described previously. d thereafter alumina from the resultant solution by introducealhum ox de and alumina are tw r p ing an acidic material thereinto, dissolving the from the Solutlon, and the galllum fiXld-e 15 co-precipitated gallium oxide and alumina in an er d to gallium in the manner previously Set aqueous alkali metal hydroxide solution, electrof t In this Way t e gallium Content of the depositing part of the dissolved gallium from the Spe e c y e is c e d s gallium resultant solution as metallic gallium, thereafter together with additional gallium oxide from the 40 forming dditi ed queou alkali metal alumisolution that was mixed with the spent electrot l ti t ining dissolved gallium in Y goes to the production of furthe which the atomic ratio of dissolved aluminum to electrolyte from which metallic gallium is to be dissolved lli 'i r at than 100:1 by mixing extractedthe said electrolyte with further alkali metal In t S p mentioned above of co-plecipitataluminate solution containing dissolved gallium, ing the alumina and gallium oXide, Carbon and employing the resultant mixture in the said OX e (W h y be in e fOI'm Of'gaS, Carbonic second mentioned step in further operation of acid, or sodium bicarbonate) is the acidic matethe process. rial preferred as the precipitant. The precipi- RALPH WALDO BROWN.

tate produced by such use of carbon dioxide contains a substantial proportion of combined alkali metal and carbon dioxide, apparently in the form REFERENCES CITED of an alkali metal aluminum carbonate The following references are of record in the though the precipitate obtained can be dissolved file of this Patent! in an alkali metal hydroxide solution to produce UNITED STATES PA'I'ENTS the solution from which metallic gallium is to he precipitated, I have found that the precipii gi gifi et a1 Oct i tate can be dissolved much more readily if it 663167 1900 has first been heated at a temperature of at least 300 0. to drive out carbon dioxide. By that 6 g g ggg ggg ffi ggy-2g procedure. alkali metal aluminate is apparently I formed which dissolves readily in aqueous solug ig gg i g tions and thus permits the solvent to reach the 2320773 Fink et a] Jun'e 1943 gallium oxide quickly.

, The duration of the heating operation depends 2361143 I Leute et 1944 on such factors as the proportion of combined RE N PATENTS carbon dioxide which is to be driven off, the tem- Number Country Date -perature employed, the physical state of the 331,520 Great Britain Oct 6, 1932 material heated, and cost considerations. In 3 5 Great Britain Jan 31, 1935 general, the higher the temperature at which the precipitate is heated, the shorter the period re- OTHER REFERENCES quired for. removing a given amount of carbon Friend: Textbook of Inorganic Chemistry, vol. dioxide. Grdinarily a temperature of 350-600 4 (1917'),p. 145.

C., and a heating period from one-half hour to Caven and Lander: Systematic Inorganic four hours are preferred. I 15 Chemistry, pp. 158-160 (1932). 

1. THE PROCESS OF PRODUCING GALLIUM COMPRISING THE STEPS OF FORMING AN AQUEOUS ALKALI METAL ALUMINATE SOLUTION CONTAINING DISSOLVED GALLIUM, DECREASING THE ATOMIC RATIO OF ALUMINUM TO GALLIUM IN THE RESULTANT SOLUTION BY INSOLUBLIZING SUFFICIENT OF THE DISSOLVED ALUMINUM VALUES OF THAT SOLUTION AS CALCIUM ALUMINATE THAT THE ATOMIC RATIO OF DISSOLVED ALUMINUM TO DISSOLVED GALLIUM IN THE SOLUTION LIES IN THE RANGE OF FROM 25:1 TO 100:1, SUBSEQUENTLY CO-PRECIPITATING GALLIUM OXIDE AND ALUMINA FROM THE SAID SOLUTION BY INTRODUCING AN ACIDIC MATERIAL THEREINTO, DISSOLVING THE CO-PRECIPITATED GALLIUM OXIDE AND ALUMINA AN AQUEOUS ALKALI METAL HYDROXIDE SOLUTION, ELECTRODEPOSITING PART OF THE DISSOLVED GALLIUM FROM THE RESULTANT SOLUTION AS METALLIC GALLIUM, THEREAFTER MIXING THE GALLIUM-BEARING ELECTROLYTE FROM THE LAST-MENTIONED STEP WITH ADDITIONAL AQUEOUS ALKALI METAL ALUMINATE SOLUTION CONTAINING DISSOLVED GALLIUM, AND EMPLOYING THE RESULTANT MIXTURE IN THE SAID SECOND-MENTIONED STEP IN FURTHER OPERATION OF THE PROCESS. 